This invention relates in general to an echo producing or reverberation system in which an audio input can be reproduced and delayed according to the desires of the listener and, in particular, to an electronic system for artificially producing reverberations or echoes of varying time interval and frequency of occurrence from any electro-audio signal source.
More specifically, this invention relates to a solid state reverberation or echo producing system adapted to be coupled to any electronic audio signal source for reproducing a delayed secondary signal echoing the primary input signal in accordance with any desired delay time or repetition of the echo.
In the entertainment field it is sometimes desirable to enhance not only vocal and instrumental recordings, but rhythm patterns through the use of echo effects such as produced in an echo chamber. This echo reproduction has not only been used by many recording artists and groups, but in some instances has been used to such an extent that it has become the style of certain entertainers. Such echo effects have normally been produced by recording the selection in an echo chamber, and it is many times desirable to enhance existing recordings by re-recording the selections with an echo type background or to listen to the record with a selective echo effect.
Various electrical sound delaying devices have been developed in order to provide such a stereophonic sound effect or an echo effect to music or speech simulating a large auditorium, or the effect produced by recording in an "echo chamber" . Such systems have utilized a tape or wire recorder coupled into the speaker circuit from a microphone and in this manner, as the audio signals are passed from the microphone, they are coupled to a recording head which records the signals onto a storage medium which is running in an endless loop. As the primary signal is recorded onto the recording medium, the medium advances and at a predetermined time the signals are picked up by a playback head which couples the signals to the speaker, thereby producing a time delayed reproduction or echo of the original audio input. While such systems have been utilized successfully in certain applications, they are limited by such things as difficulty encountered when attempting to adjust the delay or echo time due to the physical and electronic constraints of the system and cannot reproduce or provide an echo effect for signals less than a predetermined time period. In addition, such systems lose reproduction quality by requiring that the signal be recorded onto an intermediate storage medium.
One of these problems encountered with the echo producing systems utilizing a tape recorder or magnetic recording medium is that when the recording head is placed close to the readback or playback head, the relatively large current amplitudes of the recording head produce a leakage flux which is intercepted by the readback or playback head coil and appears as a noise signal. If the recording head is placed too closely in physical proximity to the playback head, the noise signals are so great that the echo reproduction is unacceptable. Therefore, such systems cannot be utilized closer than a predetermined minimum physical spacing between the units. Since the distance between the recording head and the playback head defines the time delay or the echo time, the only type of echoes which may be satisfactorily produced on such a system are those wherein the desired time delay period is greater than the minimum predetermined spacing between the recording and the playback head is taking into consideration the speed at which the tape is moved between the two heads. Shielding has been attempted to minimize this noise problem, but greatly increases the cost of the echo system. While shielding has been found to alter the limits of the problem, it does not provide a satisfactory solution.
In addition to the timing and "noise" problem, it has been found that the endless loop of recording medium utilized to provide the buffer for the delayed or echo signal is difficult to load or reload. In order to utilize both sides of the recording medium, the recording medium must be spiral-wound in a loop of a predetermined length with an exact number of loop turns to operate reasonably smoothly. Therefore, only a relatively small number of loop turns can be used. If the tape is shortened or lengthened, as in making a repair splice, the tape cannot be adjusted to the loop change and damaging binding action results. One attempt to solve this problem has been through the use of a spiral-wound loop body wherein automatic self-adjusting take-up mechanisms are used which, obviously, adds to the cost of such a system and have not proven to be entirely satisfactory.
A further problem encountered with such electromechanical systems is the cost and maintenance of the recording and playback heads. Since these systems utilize an intermediate storage or buffer medium, such as the recording tape, the wear on the tape and the problem of tape breakage create additional problems which lend themselves to unsatisfactory operation of these prior art systems.